The present invention is directed generally to automatic actuation of fluid flow control valves and more particularly to a new and improved automatic actuation system for a valve having compound movement during the opening and closing operation.
The invention will be particularly described herein with reference to a ball valve having a compound closure movement, of the type disclosed in a copending application Ser. No. 886,649, filed Mar. 15, 1978. Briefly, this ball valve comprises a body which defines a valve chamber in which a rotary fluid control ball member is contained. The body also defines a pair of passages which communicate with the valve chamber on opposing sides thereof, until the ball member having a through bore for connecting the passages when the ball is in the "valve open" position. The valve chamber is designed such that converging annular wall or seating surfaces are provided where the passages open into said chamber. Generally annular sealing rings or seats for the ball are held in surrounding relation to these converging surfaces and the ball to form a seal. A control shaft is joined with the ball and a first lever is provided for moving the ball with respect to the seal rings and seating surfaces to achieve a wedging action or alternately to relieve the wedging action to allow free rotation of the ball to its open or closed position as desired. A second control lever mounted on the valve shaft achieves this latter rotation of the ball type flow control member. Consequently, the preferred sequence of operation of the valve is generally as follows: raise-rotate-lower, for each opening or closing operation of the valve.
It is important to assure that such a compound movement valve is operated in the proper sequence, as described above, to prevent possible damage to the valve or to the system of which the valve is a part. Typically, such valves are used in systems where relatively high pressures and/or temperatures are encountered, such that failure of such a valve may have highly undesirable or even dangerous conseqences.